US11570829B2 - Method and apparatus for supporting device to device communication for wireless devices - Google Patents
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- US11570829B2 US11570829B2 US17/116,312 US202017116312A US11570829B2 US 11570829 B2 US11570829 B2 US 11570829B2 US 202017116312 A US202017116312 A US 202017116312A US 11570829 B2 US11570829 B2 US 11570829B2
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W76/00—Connection management
- H04W76/10—Connection setup
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W92/00—Interfaces specially adapted for wireless communication networks
- H04W92/16—Interfaces between hierarchically similar devices
- H04W92/18—Interfaces between hierarchically similar devices between terminal devices
Definitions
- the present invention pertains in general to wireless communications, and in particular to methods and apparatuses for supporting device to device communication for wireless devices.
- a legacy cellular user equipment can communicate with another UE through a base station (BS) irrespective of the proximity (e.g. distance) between them.
- BS base station
- Such communication typically involves the use of licensed resources which incurs additional cost and consumes extra time and energy in order to establish a connection over the cellular network.
- device-to-device communication for example side link (SL) communication
- SL communication can be performed with or without assistance of a BS, which can potentially improve latency and battery life of the UE.
- use of the unlicensed band for SL (SL-U) can provide some benefits without using expensive licensed spectrum thereby reducing the cost of transmission.
- SL can be regarded as a secondary radio access technology and can coexist with the primary cellular communication on the UE without additional radio hardware.
- the existing SL protocol is designed to operate only when both the UE's transmitter and receiver are relatively free from cellular link responsibilities. For example, this can occur when the UE is in cellular discontinuous reception (DRX) mode.
- DRX discontinuous reception
- a UE can listen for a SL grant or SL message periodically, based on its SL-DRX cycle on the dedicated time slots. This is referred to as a SL paging occasion (SL-PO).
- SL-PO SL paging occasion
- the locations of the SL-POs can be specified in true time, based on the unique ID of the UE.
- SL message exchange can follow a synchronous hybrid automatic repeat request (HARQ) process until completion of the message exchange.
- HARQ synchronous hybrid automatic repeat request
- the SL protocol should be designed to operate on half-duplex frequency division duplex (HD-FDD) devices and should use the existing single radio. Further, the SL protocol should also be designed to meet reasonable latency and battery life targets with respect to the UEs and provide a level of flexibility for latency-power trade-off.
- HD-FDD half-duplex frequency division duplex
- SRC source
- DST destination
- existing SL protocols require the SRC UE to acquire the location of the DST UE's SL-PO from the SL server. This can be accomplished for example, by obtaining the DST UE's ID and the SL-DRX period.
- existing SL protocols cannot always be used since the requirements, for example those as noted above, cannot be met at least in some circumstances.
- the two UEs would not be synchronized and thus would be unable to communicate using SL.
- the SRC UE does not have access to the SL server and therefore, would not be able to determine the location of the DST UE's SL-PO.
- An object of embodiments of the present invention is to provide a method and apparatus for supporting device to device communication between wireless devices.
- a method that includes repeatedly transmitting, by a source user equipment (SRC UE), SL communication information and receiving, by the SRC UE from a destination UE (DST UE), a response to the SL communication information.
- the SRC UE continues repeated transmission of SL communication information until the response is received.
- the SL communication information includes a SL sync signal.
- the SL communication information includes SL-data.
- the SL-data is one or more of: a SL timing request message, a SL sync request message, configured using orthogonal frequency division multiplexing and configured using quadrature phase shift keying.
- the SRC UE is synchronized with the DST UE and the SL communication information includes SL-data and excludes a SL sync signal.
- the SRC UE is unsynchronized with the DST UE, wherein the SL communication information includes the SL sync signal and the SL-data, wherein the SL sync signal is transmitted prior to the SL-data.
- the SL communication information is a single synchronization signal, the single synchronization signal configured at least in part as a SL sync signal and a SL timing request.
- the SL communication information comprises a SL sync signal and SL data, wherein the SL sync signal is transmitted prior to the SL data.
- the SRC UE determines timing of transmission of the SL communication information by decoding the SL communication information.
- the DST UE is configured to monitor for the SL communication information within a time window.
- transmission of the SL communication information is repeated multiple times based on a maximum number of attempts to transmit and a time between the attempts.
- the response includes one or more of: precise timing, macro timing, a synchronization method, an identifier (ID) of the DST UE, SL-discontinuous reception (SL-DRX) information and receiver (Rx) beacon information.
- receiving by the DST UE is performed during a receiver (Rx) sync time window, wherein the Rx sync time window is configured to occur periodically or after a fixed duration or continuously for a DST UE as desired by the application/use.
- transmission of the SL communication information is performed in cooperation with a receiver (Rx) beacon.
- a server provides the DST UE with one or more synchronization errors including: Coarse Sync Timing Error, DST UE Sync Error, SRC UE Sync Error, and Time of Flight.
- a length of time that the DST UE monitors for the SL communication information is equal to or greater than a sum of the synchronization errors.
- the Coarse Sync Timing Error is determined based on a synchronization method.
- a user equipment including a processor and machine readable memory, which stores machine executable instructions.
- the machine executable instructions which when executed by the processor, configures the UE to repeatedly transmit SL communication information and receive, from a destination UE (DST UE), a response to the SL communication information.
- the UE is configured to continue repeated transmission of SL communication information until the response is received.
- Embodiments have been described above in conjunctions with aspects of the present invention upon which they can be implemented. Those skilled in the art will appreciate that embodiments may be implemented in conjunction with the aspect with which they are described, but may also be implemented with other embodiments of that aspect. When embodiments are mutually exclusive, or are otherwise incompatible with each other, it will be apparent to those skilled in the art. Some embodiments may be described in relation to one aspect, but may also be applicable to other aspects, as will be apparent to those of skill in the art.
- FIG. 1 illustrates an example of resolving a synchronization issue residing in SL communication by transmitting a SYNC signal before SL data according to the prior art.
- FIG. 2 A illustrates a 3-step approach for a timing request solution supporting SL communication, in accordance with embodiments of the present disclosure.
- FIG. 2 B illustrates a 2-step approach for a timing request solution supporting SL communication, in accordance with embodiments of the present disclosure.
- FIG. 3 A illustrates an example of a required Rx SYNC window for the DST UE based on a single SL SYNC attempt by the SRC UE, in accordance with embodiments of the present disclosure.
- FIG. 3 B illustrates an example of a required Rx SYNC window for the DST UE based on three SL SYNC attempts by the SRC UE, in accordance with embodiments of the present disclosure.
- FIGS. 4 A to 4 C illustrate examples of placing a SL-PO in parallel to the Rx SYNC window and placing the SL-PO before the Rx SYNC window, in accordance with embodiments of the present disclosure.
- FIG. 5 illustrates an example scenario wherein the Rx SYNC window occurs every second SL-PO, in accordance with embodiments of the present disclosure.
- FIG. 6 illustrates a method for supporting side link communication, in accordance with embodiments of the present disclosure.
- FIG. 7 is a schematic diagram of an electronic device according to embodiments of the present disclosure.
- D2D communication can be enabled in multiple ways, and it can be defined as device to device (D2D) communications.
- D2D communication has been defined as sidelink (SL) communications as an example.
- SL sidelink
- SL communications to a more general version of D2D communications.
- D2D communications for example SL communications, using unlicensed bands, it would be readily understood how to apply such embodiments when using licensed bands as well.
- the term source (SRC) device is used to define a device, for example a user equipment (UE), which initiates D2D communication with a destination (DST) device, for example a UE.
- DST device is used to define a device, for example a UE, which receives a request for D2D communication from a SRC device, for example a UE. It will be readily understood, that both the SRC device and the DST device are configured in order to perform both transmission and reception of information that can enable at least D2D communications.
- Rx Sync window is used to define a time range that a destination device (e.g. user equipment (UE)) monitors for a side link (SL) synchronization signal.
- UE user equipment
- SL side link
- synchronization and “precise synchronization” are interchangeably used to define synchronization between devices (e.g. UEs) where a synchronization error is within the cyclic prefix (CP), for example 5 ⁇ s.
- CP cyclic prefix
- coarse sync and “coarse synchronization” are interchangeably used to define synchronization between devices (e.g. UE) where synchronization error is within the maximum practical Rx sync window.
- the present disclosure provides methods and apparatuses for supporting device to device (D2D) communication, for example side link (SL) communication, between wireless devices.
- D2D device to device
- SL side link
- the present disclosure provides methods and apparatuses for (D2D) communication on wireless bands when a source UE (SRC UE) and a destination UE (DST UE) are unsynchronized.
- SRC UE source UE
- DST UE destination UE
- D2D communication can be enabled in multiple ways, and it can be defined as device to device (D2D) communications.
- D2D communication has been defined as side link (SL) communications as an example.
- SL side link
- Existing protocols for SL work only where the SRC UE and the DST UE are synchronized to the same cellular synchronization signals and the SRC UE knows the location of the DST UE's SL paging occasion (SL-PO).
- the existing SL protocols cannot be used in some circumstances. For example existing SL protocols cannot be used when at least one of the SRC UE and the DST UE is out of cellular coverage or when the UEs are connected to different unsynchronized base stations (i.e. synchronization problem) or when the SRC UE is not able to access the SL server and therefore does not know the location of the DST UE's SL-PO (i.e. unknown SL-PO location problem). As such, efforts have been made to overcome the limitations of the existing SL protocols, in terms of synchronization and unknown SL-PO location.
- Attempts to overcome the synchronization issue residing in the existing SL protocols can include the use of a long SL Rx synchronization window and a variety of different coarse synchronization methods.
- FIG. 1 illustrates an example of resolving a synchronization issue residing in SL communication by transmitting a SYNC signal before SL data.
- Long-Term Evolution (LTE) device-to-device (D2D) communication uses a technique where the SRC UE 110 transmits an SL synchronization (SYNC) signal before sending SL-data.
- SYNC SL synchronization
- the DST UE 120 Upon receiving the SL Sync signal, the DST UE 120 will synchronize to the SRC UE 110 using the received SL Sync signal before trying to decode the SL-data.
- the DST UE 120 will listen for the SL Sync signal within a certain time range, hereinafter referred to as the SL Rx Sync window.
- An example of the SL Rx Sync window (e.g. SL Rx Sync window 130 ) is also illustrated in FIG. 1 .
- a problem with this method is that the SRC UE 110 and DST UE 120 need to be coarse synchronized in advance.
- coarse synchronization may define synchronization between devices (e.g. between UEs) where a synchronization error is within a maximum practical Rx sync window. Otherwise, for example, the SL Rx Sync window 130 would be impractically long.
- the length of the SL Rx Sync window (e.g. SL Rx Sync window 130 ) needs to be long enough to account for timing errors between the SRC UE 110 and DST UE 120 .
- the timing errors may include, but not limited to, one or more of the following:
- the length of the SL Rx SYNC window can be defined as being substantially equal to or greater than the sum of Coarse Sync Timing Error and DST UE Sync Error and SRC UE Sync Error and Time of Flight.
- the SL Rx Sync window should be minimized.
- the value of coarse sync timing error, DST UE sync error, SRC UE sync error and time of flight should be known.
- some of these values, such as DST UE sync error are unknown to the DST UE.
- the method of minimizing the SL Rx Sync window (by the DST UE) is unknown and therefore means for, at least in part, providing power optimization (e.g. minimizing power consumption) is also unknown.
- SL side link
- PSS primary synchronization signals
- SSS secondary synchronization signals
- MIB master information block
- GNSS global navigation satellite system
- SL side link
- the LTE cellular synchronization signals can be used to provide synchronization for SL.
- the accuracy of these synchronization signals depends on whether the SRC UE and the DST UE are synchronized to the same cell (e.g. same base station). If the SRC UE and DST UE are synchronized to the same cell, there is no sync timing error and therefore, precise timing can be provided. If the SRC UE and the DST UE are synchronized to different base stations, the level of synchronization between the two UEs would depend on cell synchronization. LTE does not require cells to be synchronized but, they can be synchronized.
- PSS primary synchronization signals
- SSS secondary synchronization signals
- MIB master information block
- GNSS Global Navigation Satellite System
- GNSS-based synchronization can provide up to 40 ns of synchronization.
- this method of synchronization is not a power efficient method.
- this method only works outside and can be an expensive method as it requires additional hardware, for example for accessing the GNSS.
- SL beacons In LTE device to device (D2D) communications, some UEs are assigned to act like SL beacons by periodically transmitting side link primary synchronization signals (SPSS) and side link secondary synchronization signal (SSSS) followed by a broadcast message which includes the system frame number (and in some configurations a hyper frame number, however this is currently not a feature of LTE D2D communications).
- SPSS side link primary synchronization signals
- SSSS side link secondary synchronization signal
- This method of assigning a UE to act as a SL beacon can be also used for SL.
- Whether or when a UE becomes a SL beacon can be pre-configured or self-elected or directed by the SL server. For example, the UE may self-elect to become a SL beacon when it does not receive synchronization signals from any other sources.
- This method can provide good accuracy unless the SRC UE is not synchronized to the same source as the UE acting as a SL beacon UE. If the SRC UE is not synchronized to the same source as the UE acting as the SL beacon, the accuracy can depend on how closely the SRC UE and UE acting as a SL beacon are synchronized.
- Assigning some UEs to act like SL beacons for SL can have some disadvantages.
- One of the disadvantages is energy consumption. Significant battery power is required for UEs to become SL beacons.
- the synchronization signals should be transmitted at known times; however, as SL implementation is based on the constraints of using a shared single HD-FDD radio, it may not be possible to transmit the synchronization signals at precise times.
- each of the above coarse synchronization methods have at least some issues or limitations therewith for providing synchronization for SL. Further, each of the above coarse synchronization methods can require the UE to already have information relating to SL-PO location.
- the SL-PO location can be predefined.
- the UEs e.g. SRC UE and DST UE
- This action can be performed by manually pre-configuring the UEs with the possible DST UE IDs and the associated possible extended discontinuous reception (eDRX) values.
- this pre-configuration method may not always be feasible. For example, when the number of UEs in the group is large, the method may not be scalable as the SRC UE needs to try every possible UE ID in order to find out which DST UE is reachable. Furthermore, this pre-configuration method may not work in conditions where the SL-DRX is dynamic.
- Another solution for overcoming the unknown SL-PO location is to configure a UE to act as a SL server.
- a UE is configured to act as a SL server, the UE would need to be operating for most of the time and thus, would need a larger battery or potentially a direct power supply (e.g. alternating current (AC) power supply).
- AC alternating current
- non-homogeneous or heterogeneous sets of UEs would render such deployment even more complicated.
- the SRC UE can require access to the UE SL server, however, such access is not possible if the SRC UE does not know the location of the SL-PO of the UE SL server.
- a mesh protocol can be used on top of the SL protocol such that the access to the SL server can be made through substantially any UE which is part of the mesh.
- this method also has a potential problem. For instance, the SRC UE can still require access to at least one UE connected to the mesh. However, such access is not possible if the SRC UE does not know the location of the SL-PO of the SL server.
- the methods and apparatuses can support SL communication where a source (SRC) or destination (DST) UE is unsynchronized.
- SRC source
- DST destination
- D2D communications for example, SL communications
- the timing request solution can resolve both the synchronization problem and the unknown SL-PO location problem which has been noted above.
- FIGS. 2 A and 2 B illustrate examples of the timing request solution supporting SL communication, in accordance with embodiments of the present disclosure. Specifically, FIG. 2 A illustrates a 3-step approach and FIG. 2 B illustrates a 2-step approach of the timing request solution supporting SL communication.
- the timing request method can be appropriate for an unsynchronized UE which has no knowledge about the SL-PO (e.g. location of the SL-PO).
- the unsynchronized UE e.g. SRC UE 202
- blindly and repeatedly transmits a SL-Sync signal e.g. SYNC 210
- a SL timing request message e.g. SL-TimeReq 220
- a timing response message e.g. SL-TimingRsp 230
- DST UE e.g. DST UE 201
- OoCC out of cellular coverage
- the SRC UE 202 has no timing information, the SRC UE needs to repeatedly transmit the SL-Sync signal (e.g. SYNC 210 ) and the SL timing request message (e.g. SL-TimeReq 220 ) until the SL-SYNC signal is received by a DST UE within the DST UE's Rx Sync window (e.g. Rx Sync Window 203 ).
- the SL timing request message e.g. SL-TimeReq 220
- each DST UE that correctly receives the SL-Sync signal and SL timing request message transmits a timing response message (e.g. SL-TimeRsp 230 ) in response to the receipt of the SL-Sync signal and SL timing request message.
- the timing response message can include one or more of the following pieces of information:
- timing request method may consume significant power, the method only needs to be done once at power-up and may not be required for re-synchronization.
- the unsynchronized UE e.g. SRC UE 205
- the SL timing request message e.g. SL-TimeReq 220
- a special Sync signal e.g. TimeReqSync 240
- the special Sync signal can be configured as a combination of the SL-Sync signal (e.g. SYNC 210 ) and the SL timing request message (e.g. SL-TimeReq 220 ). This can be envisioned as a 2-step approach for the timing request method illustrated in FIG. 2 B .
- the DST UE Upon detecting the special Sync signal (e.g. TimeReqSync 240 ) during the Rx Sync Window 206 , the DST UE (e.g. DST UE 204 ) broadcasts the timing response message (e.g. SL-TimeRsp 230 ).
- the 2-step approach allows synchronization requests to be sent more frequently.
- the timing request method may be enhanced using optional receiver (Rx) beacons.
- Rx beacons can be considered to be UEs with larger battery capacity or direct power supply (e.g. AC powered) that are listening for the SL Sync signals more often.
- the UEs are listening for SL Sync signals more often by being configured with no SL-DRX, shorter SL-DRX cycles or long Rx Sync windows. These configurations can increase the probability that the SRC UE's timing request (e.g. SL-TimeReq 220 ) will be responded to.
- the out of cellular communication UE can learn about an Rx beacon in two ways. For example, information regarding the Rx beacon can be received directly from the SL server or via a mesh SL-UE. As another example, the information regarding the Rx beacon can be received through the SL timing response message (e.g. SL-TimeRsp 230 ).
- the out of cellular communication UE can request the SL server to declare a UE as a Rx (or Tx) beacon.
- Rx beacons or Tx beacons are known and the advantages can include for example, the feature that Rx beacons do not create traffic or interference, and that Rx beacons can be more efficient with power consumption as they only receive communications and do not transmit.
- UEs may need to be periodically re-synchronized, for example due to XTAL error.
- the SRC UE knows at least one DST UE's SL-PO location and optionally, a Rx beacon's SL-PO location which can be used for the SRC UE's re-synchronization.
- the timing request solution can be more energy efficient compared to other approaches such as GNSS and deep coverage PSS/SSS/MIB.
- SL Sync signal can cause a waste of power as the UE would decode the SL-Data that is not intended for it.
- the UE may miss the SL Sync signal intended for it, if the correct SL Sync signal is transmitted or broadcasted while the UE is decoding the SL-Data intended for another UE.
- D2D communication for example SL communications
- DST UEs e.g. assigning a unique or pseudo-unique SL Sync signal to each DST UE
- SL Sync signals are not uniquely assigned to all UEs as it may not be practical, depending on the SL Sync signal design, to assign unique SL Sync signals to all UEs.
- assigning a pseudo-unique SL Sync signal can be acceptable (i.e. some overlap is acceptable) as the probability of decoding a SL Sync intended for another UE will be significantly decreased with pseudo-unique SL Sync signal assignment.
- the probability of decoding a SL Sync intended for another UE can be further reduced by ensuring that a unique SL-PO is assigned to the UE such that SL-PO is unique with respect to the close SL-POs, as the risk of misdetection (or collision) is higher between close SL-POs. Since there are a finite number of SL-POs, each SL-PO associated with the UE can be given a unique SL Sync signal, especially with respect to SL-POs that are closely located. Given that the location of the SL-PO is already known, the SRC UE can know which SL Sync to transmit.
- the SL Rx Sync window should be minimized in order to minimize power consumption of the UE.
- some of synchronization errors present may be provided to the DST UE by the SL server to aid with the mitigation of these synchronization errors.
- the synchronization errors provided by the SL server can help the DST UE to reduce the SL Rx Sync window.
- SL communications can be supported wherein given that the SL Rx Sync window is equal to or greater than the sum of Coarse Sync Timing Error, DST UE Sync Error, SRC UE Sync Error, and Time of Flight, the DST UE can know or manage each of the associated synchronization errors as follows:
- D2D communications for example SL communications
- SL Rx Sync window can be reduced by performing multiple SL attempts.
- multiple SL attempts may also allow re-synchronization of the UE to be performed less frequently.
- power consumption associated with the UE can be expected to be high. For instance, for XTAL of 10 ppm (e.g. oscillator frequency stability of 10 ppm), 10 ⁇ sec of time error would be accumulated in every second.
- Re-synchronization using PSS/SSS/MIB at low SNR or GNSS can take up to 10 seconds.
- the multiple SL attempts solution requires the SRC UE to send multiple SL Sync signals and SL data attempts in quick succession.
- the maximum number of attempts e.g. MaxAttempts 310
- the time between the attempts e.g. TimeBetweenAttempts 320
- FIGS. 3 A and 3 B illustrates a reduction of the required Rx Sync window for the DST UE by increasing the number of SL attempts by the SRC UE, in accordance with embodiments of the present disclosure.
- FIG. 3 A illustrates the Rx Sync window for a single sync attempt
- FIG. 3 B illustrates the Rx Sync window for 3 sync attempts.
- the required Rx Sync window for the DST UE can be reduced from 24 ms to 8 ms by increasing the number of attempts sent by the SRC UE from 1 to 3.
- the SRC UE 302 transmits a single Sync signal and a single SL Data signal and in order to ensure that the DST UE 301 receive these signals the SL Rx Sync window has a particular duration, for example 24 ms.
- the Rx Sync window 330 can be smaller than the Rx Sync window 303 illustrated in FIG. 3 A .
- the time between the attempts is equal to the DST SL Rx Sync window 330 .
- the DST SL Rx SYNC window 330 must be at least long enough to send the SL SYNC signal (1 ms), detect the SL Sync signal (1 ms), send SL data (1 ms), decode the SL Data (3 ms), send an SL Acknowledgement (1 ms) and decode the SL Acknowledgement (1 ms).
- the values defined in parentheses for each of the above noted activities performed by the respective UE are practical times required for each respective activity.
- the length of the DST SL Rx Sync window 330 must be at least 8 ms to allow for all of the above noted activities to be completed during the Rx Sync window.
- the time between the attempts e.g. TimeBetweenAttempts 320
- the time between the attempts equals to 8 ms.
- the power required for the SRC UE when transmitting n sync attempts instead of 1 sync attempt is less than the power required when using a longer Rx Sync window at the DST UE, due to the less frequent SL Data transmissions.
- FIGS. 4 A to 4 C illustrate examples of placing a SL-PO in parallel to the Rx SYNC window and placing the SL-PO before the Rx SYNC window, in accordance with embodiments of the present disclosure.
- FIG. 4 A illustrates transmissions of the DST UE 402 and the SRC UE 401 when the SL-PO and Rx Sync window are in parallel and the DST UE and the SRC UE are not synchronized.
- FIG. 4 B illustrates transmissions of the DST UE 402 and the SRC UE 401 when the SL-PO and Rx Sync window are in parallel and the DST UE and the SRC UE are synchronized.
- FIG. 4 C illustrates transmissions of the DST UE 402 and the SRC UE 401 when the SL-PO is located before the Rx Sync window and the DST UE and the SRC UE are synchronized.
- D2D communications for example SL communications
- the SRC UEs may be provided with an option to not send a SYNC signal before the SL-Data when the SRC UE knows it is synchronized with the DST UE.
- This configuration can reduce latency and reduce power consumption by the UE.
- This method can be used for example when both the SRC UE and DST UE are using PSS/SSS/MIB synchronization method associated with the same base station.
- the SRC UE can choose to skip sending a Sync signal and transmit SL-Data only. In such embodiments, only if the SL-Data transmission fails (i.e. only if the SRC UE does not receive an acknowledgement message from the DST UE), the SRC UE transmits a Sync signal followed by SL-Data at the next available Rx Sync window. If an acknowledgement message is expected before the end of the Rx Sync window, the SRC UE does not even need to wait for the next SL-DRX cycle.
- skipping transmission of the Sync signal can be beneficial when the SRC UE prioritizes extending its battery life over SL latency. Skipping transmission of the Sync signal can also be beneficial when the SRC UE has some form of a-priori knowledge that the DST UE is likely to be synchronized with it (e.g. when the two UEs are in the same cell).
- the SL server can optionally hold the information whether the SRC UE and DST UE are synchronized (e.g. PSS/SSS/MIB and corresponding cell ID).
- FIG. 5 illustrates a non-limiting example scenario where the Rx Sync window occurs for every second SL-PO, in accordance with embodiments of the present disclosure. Referring to FIG. 5 , the period of the SL-PO 520 is half that of Rx Sync window 510 .
- the SL server can provide the SRC UE with information regarding the Rx Sync window location.
- D2D communications for example SL communications
- a UE is willing to use extra power in order to determine the timing of the transmission of the SL-Data signal (e.g. less than 1 SF timing) by decoding the SL Sync signals from any UE.
- This decoding of the Sync signal can provide timing accuracy equal to or less than the sum of the SRC UE Sync Error and the Coarse Sync Timing Error. If the sum of the SRC UE Sync Error and the Coarse Sync Timing is greater than 1 ms, timing of the SL-Data transmission may not be inferred unless the SL Sync signal is restricted to be transmitted on a certain SF (e.g. the 5th SF of every frame). In a case where the SL Sync signal is restricted to be transmitted on certain SF, the SL-Data transmission timing can be determined to be within a 10 ms radio frame.
- the SRC UE can directly transmit the SL-Data on the SL-PO of the DST UE without transmitting an SL Sync signal.
- This method can be used if the SL Sync signal comes from a UE that is in cell coverage or an out of cellular coverage UE that in turn receives the SL Sync signal from a UE that is within cell coverage. An indication of this qualification of the above can be required in order to validate the SL Sync signal.
- the method includes repeatedly transmitting, by a source user equipment (SRC UE), SL communication information 610 and receiving, by the SRC UE from the DST UE, a response to the SL communication information 620 .
- the SRC UE continues repeated transmission of SL communication information until the response is received.
- the SL communication information comprises an SL sync signal and an SL timing request message, the SL sync signal being transmitted prior to the SL timing request.
- the SL communication information is a single synchronization signal, the single synchronization signal configured at least in part as a SL sync signal and a SL timing request message.
- FIG. 7 is a schematic diagram of an electronic device 700 that may perform any or all of the steps of the above methods and features described herein, according to different embodiments of the present invention.
- a UE may be configured as the electronic device.
- the device includes a processor 710 , memory 720 , non-transitory mass storage 730 , I/O interface 740 , network interface 750 , and a transceiver 760 , all of which are communicatively coupled via bi-directional bus 770 .
- a processor 710 processor 710
- memory 720 non-transitory mass storage 730
- I/O interface 740 I/O interface 740
- network interface 750 e.g., network interface 750
- transceiver 760 e.g., the device 700 may contain multiple instances of certain elements, such as multiple processors, memories, or transceivers.
- elements of the hardware device may be directly coupled to other elements without the bi-directional bus.
- the memory 720 may include any type of non-transitory memory such as static random access memory (SRAM), dynamic random access memory (DRAM), synchronous DRAM (SDRAM), read-only memory (ROM), any combination of such, or the like.
- the mass storage element 730 may include any type of non-transitory storage device, such as a solid state drive, hard disk drive, a magnetic disk drive, an optical disk drive, USB drive, or any computer program product configured to store data and machine executable program code. According to certain embodiments, the memory 720 or mass storage 730 may have recorded thereon statements and instructions executable by the processor 710 for performing any of the aforementioned method steps described above.
- base station and network node can be interchangeably used to define an evolved NodeB (eNB), a next generation NodeB (gNB) or other base station or network node configuration.
- eNB evolved NodeB
- gNB next generation NodeB
- D2D communication can be enabled in multiple ways, and it can be defined as device to device (D2D) communications.
- D2D communication has been defined as side link (SL) communications as an example.
- SL side link
- Acts associated with the method described herein can be implemented as coded instructions in a computer program product.
- the computer program product is a computer-readable medium upon which software code is recorded to execute the method when the computer program product is loaded into memory and executed on the microprocessor of the wireless communication device.
- Acts associated with the method described herein can be implemented as coded instructions in plural computer program products. For example, a first portion of the method may be performed using one computing device, and a second portion of the method may be performed using another computing device, server, or the like.
- each computer program product is a computer-readable medium upon which software code is recorded to execute appropriate portions of the method when a computer program product is loaded into memory and executed on the microprocessor of a computing device.
- each step of the method may be executed on any computing device, such as a personal computer, server, PDA, or the like and pursuant to one or more, or a part of one or more, program elements, modules or objects generated from any programming language, such as C++, Java, or the like.
- each step, or a file or object or the like implementing each said step may be executed by special purpose hardware or a circuit module designed for that purpose.
Abstract
Description
-
- Coarse sync timing error is an error due to the coarse timing method (which is illustrated elsewhere in the present disclosure). Each coarse timing method can have different amounts of error associated therewith.
- DST UE sync error is a timing error in the DST UE (e.g. DST UE 120). This error usually occurs due to crystal reference oscillator (XTAL) accuracy, for example the accuracy of a crystal oscillator. Generally, the DST UE sync error is equal to approximately (DST XTAL accuracy)×(Time since last Coarse Sync).
- SRC UE sync error which is a timing error in the SRC UE (e.g. SRC UE 110). This error usually occurs due to XTAL accuracy. Generally, the SRC UE sync error is equal to approximately (SRC XTAL accuracy)×(Time since last Coarse Sync).
- Time of flight which is time required for transmission from the SRC UE (e.g. SRC UE 110) to the DST UE (e.g. DST UE 120). Generally, the time of flight is equal to approximately (distance between SRC UE and DST UE)/(speed of light).
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- Precise timing information: μsec timing correction to the nearest subframe (SF) and SF timing
- Macro timing information: system frame timing, similar to MIB, and hyper frame timing, similar to SIB1
- Sync method information: e.g. GNSS, PSS/SSS/MIB, transmitter (Tx) beacon, etc.
- UE ID: ID of the DST UE that may be used to calculate future SL-POs
- SL-DRX information: SL-DRX may be used to calculate future SL-POs
- Receiver (Rx) beacon information: Rx beacon ID and SL-DRX
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- Coarse Sync Timing Error depends on the synchronization method. As the maximum error should be static, the Coarse Sync Timing error can be provided to the DST UE, for example in some instances by the SL server. If the system uses a different sync method, the errors associated with the respective sync method can be provided to the DST UE.
- SRC UE Sync Error. Given the large number of potential SRC UEs, acquiring the SRC UE specific value (e.g. SRC UE specific Sync error) may not be practical. As such, a system-wide wide Maximum SRC UE Sync error can be defined in the system specifications or defined within the SL server. The SRC UE can be re-synchronized close enough to when it transmits the Sync signal in order to ensure the synchronization error of that SRC UE is equal to or less than the defined system-wide Maximum SRC UE Sync Error.
- DST UE Sync Error. As illustrated above with respect to the SRC UE Sync Error, the DST UE Sync Error can be managed by the DST UE directly by ensuring that one or both of: 1) the SL Rx Sync window is long enough; and 2) the DST UE re-synchronizes often enough to ensure the DST UE Sync Error does not make the total synchronization error exceed the SL Rx Sync Window (e.g. the DST UE's contribution to the total synchronization error is kept within the SL Rx Sync Window).
- Time of Flight: Mitigation of an error associated with the time of flight can be achieved by defining a system-wide Maximum Time of Flight by the SL server or specified with respect to the particular system.
Multiple SL Attempts
Claims (28)
Priority Applications (4)
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US17/116,312 US11570829B2 (en) | 2020-12-09 | 2020-12-09 | Method and apparatus for supporting device to device communication for wireless devices |
EP21901755.5A EP4260645A1 (en) | 2020-12-09 | 2021-12-08 | Method and apparatus for supporting device to device communication for wireless devices |
CA3201601A CA3201601A1 (en) | 2020-12-09 | 2021-12-08 | Method and apparatus for supporting device to device communication for wireless devices |
PCT/CA2021/051759 WO2022120479A1 (en) | 2020-12-09 | 2021-12-08 | Method and apparatus for supporting device to device communication for wireless devices |
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US17/116,312 US11570829B2 (en) | 2020-12-09 | 2020-12-09 | Method and apparatus for supporting device to device communication for wireless devices |
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EP4260645A1 (en) | 2023-10-18 |
US20220183091A1 (en) | 2022-06-09 |
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